In the area of wireless communications, efforts have been made to develop network infrastructures for next generation wireless communication systems. In general, these next generation wireless communication systems tend to yield increased data rates. Significantly higher data rates, however, can impose serious power implications. The power implications can result from per symbol energy decreasing linearly with increasing data rate given a fixed transmit power. Accordingly, relay based multi-hop wireless networks, which have attracted recent research and industry interest, can provide economically justifiable solutions to address the foregoing.
Relays typically operate in half-duplex mode, and thus, utilization of relays in wireless networks can yield various disadvantages that can detrimentally impact wireless communication system performance. For instance, when relays utilize half-duplex operation, they are unable to transmit and receive at the same time. Moreover, part of the radio resource can be allocated for transmission between relays and user devices (e.g., mobiles, user equipment, mobile terminals, . . . ) while a separate portion of the radio resource can be allotted for transmission between relays and base stations; the division of the radio resource can considerably reduce system throughput. These obstacles hinder development of relay based wireless multi-hop networks.
A variety of techniques have been examined that attempt to mitigate deleterious effects of relays. An example of such a technique leverages reusing channels from neighboring cells, while a further example utilizes unlicensed spectrum for the relay to mobile link. Another conventional method is to consider two-way communications where both the base station and the user device intend to transmit data to each other.
Multiple Input Multiple Output (MIMO) has also been regarded as a technique which can be utilized to realize higher data rates (e.g., gigabit data rates, . . . ) in next generation wireless communication systems. However, more antennas are likely to be installed at base stations and relays rather than user devices. Conventional MIMO relay systems typically employ a relay that oftentimes only communicates with a single user. Further, common MIMO relay systems oftentimes employ an amplify and forward relay protocol, in which the relay simply processes received signals by performing matrix multiplication, which can cause increased noise levels that can limit performance. Accordingly, there exists a need for improved MIMO relay techniques in a wireless communication system.